The present invention relates to a process for preparation of a 2-aminothiazolecarboxamide derivative represented by the following formula (I) 
wherein R1 represents straight-chain or branched C1-5 alkyl, C1-5 haloalkyl, or C3-6 cycloalkyl, and R2 represents C1-3 alkyl or C1-3 haloalkyl.
The compounds of formula (I) are used as microbicides for treating plant diseases caused by Pythiaceae or Peronosporaceae. The compounds of formula (I) were already disclosed in Korean Patent Laid-open Publication No. 94-19960 and the corresponding foreign applications, for example, U.S. patent application Ser. No. 08/287,917, JP Patent Application No. 192529 and EP Patent Application No. 94112652.6 which were filed by the present applicant.
Further, a process for preparation of 2-aminothiazolecarboxamide derivatives including the compounds of formula (I) using 2-aminothiazole carboxylic acid as an intermediate was described in Korean Patent Laid-open Publication No. 97-24120 However, this process has the disadvantage that it is not economic when applied to industrial production due to the many steps for obtaining the intermediate and the low yield.
Accordingly, the present inventors have studied to improve the prior process by solving the above mentioned problems, and as a result, have brought the present invention to completion.
The present invention relates to a process for preparation of a 2-aminothiazolecarboxamide derivative represented by the above formula (I) characterized in that an iminothiourea compound represented by the following formula (II): 
wherein R1 and R2 are defined as previously described, and R3 represents phenyl which may be optionally mono- to penta-substituted independently by chloro, methoxy, ethoxy, phenoxy or nitro, is reacted with a thiopheneacetamide compound represented by the following formula (III): 
wherein Y represents a leaving group such as chloride, bromide, etc.
The compound of formula (I) can be prepared by reacting the compound of formula (II) with the compound of formula (III) in a solvent and in the presence of a base as depicted in the following Reaction Scheme I: 
wherein R1, R2, R3 and Y are defined as previously described.
Examples of the base used in the above reaction include an organic base such as triethylamine, tributylamine, diisopropylethylamine, N,N-dimethylaniline, pyridine, 4-dimethylaminopyridine, etc., and an inorganic base such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium hydride potassium hydride, etc. The organic base is preferred, and the alkyl amine such as triethylamine, tributylamine, diisopropylethylamine, etc. is more preferred. The base can be used in an amount of 1 to 5 equivalents, preferably in an amount of 1 to 2 equivalents.
The above reaction can be carried out at the temperature between 20 and 120xc2x0 C., preferably between 40 and 80xc2x0 C., and the reaction time is suitably about 8 to 12 hours.
The solvent includes an alcohol such as methanol, ethanol, isopropyl alcohol, etc.; an aromatic hydrocarbon such as benzene, toluene, xylene, etc.; an ether such as diethylether, dioxane, 1,2-dimethoxyethane, tetrahydrofuran, etc.; a ketone such as acetone, methylethyl ketone, cyclohexanone, etc.; a nitrile such as acetonitrile, propionitrile, etc.; a halogenated hydrocarbon such as dichloromethane, 1,2-dichloroethane, chloroform, etc.; an ester such as methyl acetate, ethyl acetate, etc.; and a polar solvent such as N,N-diethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., and the alcohol is preferred.
The compound of formula (II) used as a starting material in the Reaction Scheme (I) is novel and can be prepared in accordance with the following Reaction Scheme (II): 
wherein R1, R2 and R3 are defined as previously described.
That is, the compound of formula (II) can be prepared by a process characterized in that
in Step 1 an amide compound represented by the following formula (IV) 
wherein R2 and R3 are defined as previously described, is reacted with a halogenating agent in a solvent in the presence of a base to produce an imidoylchloride compound represented by the following formula (V): 
wherein R2 and R3 are defined as previously described;
in Step 2, the resulting imidoylchloride compound of formula (V) is reacted with an isothiocyanide compound represented by the following formula (VII):
MSCNxe2x80x83xe2x80x83(VII)
wherein M represents an alkali metal such as sodium, potassium, etc., or NH4, by which the chloride group is replaced with the isothiocyanide group to produce an imidoylisothiocyanate compound represented by the following formula (VI): 
wherein R2 and R3 are defined as previously described,
in Step 3, the resulting imidoylisothiocyanate compound of formula (VI) is reacted with a primary amine compound represented by the following formula (VIII):
xe2x80x83R1xe2x80x94NH2xe2x80x83xe2x80x83(VIII)
wherein R1 is defined as previously described in the presence of a base.
In Step 1 for preparing the imidoylchloride compound of formula (V), thionyl chloride(SOCl2), phosgene(COCl2), phosphorus oxychloride(POCl3), etc. can be used as the halogenating agent. The halogenating agent is suitably used in an amount of 1 to 4 equivalents. This reaction is carried out at the temperature between xe2x88x9220xc2x0 C. and 80xc2x0 C., preferably between xe2x88x9210xc2x0 C. and 20xc2x0 C. The reaction time is suitably about 2 to 5 hours. As the base, an organic base such as pyridine, 4-dimethylaminopyridine, triethylamine, N,N-dimethyl aniline, tributylamine, etc. can be used. A mild base such as pyridine is preferred. The base is suitably used in an amount of 1 to 4 equivalents.
As the solvent, an aromatic hydrocarbon such as benzene, toluene, xylene, etc.; a halogenated hydrocarbon such as dichloromethane, 1,2-dichloroethane, chloroform, etc.; an ether such as diethylether, dioxane, 1,2-dimethoxyethane, tetrahydrofuran, etc.; a ketone such as acetone, methylethyl ketone, cyclohexanone, etc.; a nitrile such as acetonitrile, propionitrile, etc.; an ester such as methyl acetate, ethyl acetate, etc.; or a polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., preferably a halogenated hydrocarbon such as dichloroethane, chloroform, etc. can be used. In addition, N,N-dimethylfornamide can be used as a catalyst.
In Step 2, the imidoylisothiocyanate compound of formula (VI) is prepared by reacting the imidoylchloride compound of formula (V) prepared in step 1 with the isothiocyanide compound of formula (VII). The isothiocyanide compound of formula (VII) is suitably used in an amount of 1 to 2 equivalent. The reaction temperature can be between xe2x88x9220xc2x0 C. and 50xc2x0 C., preferably between 0xc2x0 C. and 20xc2x0 C., and the reaction time ranges suitably from 2 to 5 hours.
In Step 3, the iminothiourea compound of formula (II) is prepared from the imidoylisothiocyanate compound of formula (VI). In this step, the carbon atom of isothiocyanate is attacked by the amine compound of formula (VIII) in the presence of a base, by which the thiourea derivative of formula (II) is produced. The amine compound of formula (VIII) can be used in an amount of 1 to 4 equivalents, preferably 2 to 3 equivalents. This reaction can be carried out at the temperature between xe2x88x9220xc2x0 C. and 80xc2x0 C., preferably between 0xc2x0 C. and 30xc2x0 C. The reaction time is suitably from 2 to 4 hours.
The above processes according to the present invention will be more specifically explained through the following examples. As typical examples of the compounds of formula (II) according to the present invention, those described in the following table (I) can be mentioned.
The compound of formula (III) used as a starting material in the Reaction Scheme (I) is also a novel compound, and can be prepared in accordance with the following Reaction Scheme (III). 
wherein Y is defined as previously described.
That is, the compound of formula (III) can be prepared by a process characterized in that
in Step 1, an aldehyde compound represented by the following formula (IX): 
is converted into an aminonitrile compound represented by the following formula (X): 
xe2x80x83through the known Strecker Synthesis;
in Step 2, the resulting aminonitrile compound of formula (X) is reacted with a compound represented by the following formula (XI): 
xe2x80x83wherein Y is defined as previously described, in the presence of a base.
In Step 1 of the above reaction, the aldehyde compound of formula (IX) can be readily converted into the aminonitrile compound of formula (X) through the known Strecker Synthesis as stated above.
In Step 2, the thiopheneacetamide compound of formula (III) can be prepared by reacting the aminonitrile compound of formula (X) with 1 to 3 equivalents, preferably 1 to 1.5 equivalents of chloroacetyl chloride or bromoacetyl bromide of formula (XI) in the presence of a base. This reaction can be carried out at the temperature between xe2x88x9220xc2x0 C. and 80xc2x0 C., preferably between 0xc2x0 C. and 20xc2x0 C. The reaction time is suitably from 30 minutes to 2 hours.
As the base, an organic base such as pyridine, 4-dimethylaminopyridine, triethylamine, N,N-dimethyl aniline, tributylamine, diisopropylethylamine, etc., preferably pyridine or 4-dimethylamino pyridine can be used. The base can be suitably used in an amount of 1 to 3 equivalents.
As the solvent, a halogenated hydrocarbon such as dichloromethane, 1,2-dichloroethane, chloroform, etc.; an aromatic hydrocarbon such as bezene, toluene, xylene, etc.; an ether such as diethylether, dioxane, 1,2-dimethoxy ethane, tetrahydrofuran, etc.; a ketone such as acetone, methylethyl ketone, cyclohexanone, etc.; a nitrile such as acetonitrile, propionitrile, etc.; an ester such as methyl acetate, ethyl acetate, etc.; or a polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc., preferably a halogenated hydrocarbon or an aromatic hydrocarbon can be used.
The present invention is more specifically explained by the following preparation and examples. However, it should be understood that the present invention is not limited to these examples in any manner.
Into a reaction vessel were placed aniline(279.4 g, 3.0 mol) and dichloromethane(2400 g), the reaction vessel was cooled to 0xc2x0 C., and sodium hydroxide(132.0 g, 3.3 mol) dissolved in water(660 g) was slowly added dropwise thereto.
It was confirmed that the temperature of the reaction vessel was 0xc2x0 C., and then propionyl chloride(291.5 g, 3.2 mol) was added dropwise thereto for 9 hours. And then the mixture was stirred at room temperature(20xc2x0 C.) for 2 hours, and the reaction was completed. After the reaction was completed, the layers were separated, and dichloromethane was removed by distillation under the reduced pressure to produce a brown solid. The solid was recrystallized from toluene to give the title compound(434.7 g, 2.9 mol) in a yield of 97%.
1H NMR (CDCl3): xcex4 7.75(1H, s, br), 7.52(2H, d), 7.29(2H, d), 7.08(1H, t), 2.37(2H, q), 1.22(3H, t)